Air lubrication device of ship

ABSTRACT

An air lubrication apparatus of a ship includes an air ejecting unit and a restraining section. The air ejecting unit ejects air from the ship bottom. The restraining section restrains relative reduction of a thickness of an air layer which covers a center line region of the ship bottom.

INCORPORATION BY REFERENCE

The present application claims a priority based on Japanese PatentApplication No. 2010-198205 filed on Sep. 3, 2010. The disclosurethereof is incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to an air lubrication device for a shipand an air lubrication method for a ship, in which friction resistanceof a ship body is reduced by using air ejection.

BACKGROUND ART

A technique is known which reduces friction resistance of a ship body bycovering a surface of a ship bottom with a flow of air bubbles at thetime of navigation.

Referring to FIGS. 1A and 1B, a ship friction resistance reducingapparatus disclosed in Japanese Patent Publication JP 2008-114710A willbe described. Gas rooms 2 are provided in a ship bottom 1 section of aship on the side of the bow. The gas rooms 2 are provided in a shipwidth direction. Gas holding plates 5 of a pair are provided along theboth sides of the ship bottom from the bow to the stern. Gas is ejectedfrom the gas rooms 2 into water, and a flow of bubbles is generated toflow backward along the ship bottom 1. The gas holding plates 5 preventdissipation of the flow of bubbles into the sides of the ship. In thisway, friction resistance of the ship body can be reduced.

SUMMARY OF INVENTION

An air lubrication device for a ship according to a first aspect of thepresent invention includes an air ejecting unit configured to eject airfrom a ship bottom of the ship, and a restraining section configured torestrain the thickness of an air layer which covers a center line regionof a ship bottom from being relatively reduced.

The ship bottom includes a port-side region on a port side with respectto the center line region, and a starboard-side region on a starboardside with respect to the center line region. The air ejecting unitincludes N central air outlets provided in the center line region, Nport-side air outlets provided in the port-side region, and Nstarboard-side air outlets provided in the starboard-side region. The Nis a natural number. The restraining section includes another centralair outlet provided in the center line region.

The ship bottom includes a port-side region on a port side with respectto the center line region, and a starboard-side region on the starboardside with respect to the center line region. The air ejecting unitejects the air from the center line region, the port-side region, andthe starboard-side region. The restraining section includes a port-sidewall surface provided between the center line region and the port-sideregion to restrain movement of the air from the center line region tothe port-side region, and a starboard-side wall surface provided betweenthe center line region and the starboard-side region to restrainmovement of the air from the center line region to the starboard-sideregion.

The ship bottom includes a port-side region on a port side with respectto the center line region, and a starboard-side region on a starboardside with respect to the center line region. The air ejecting unitejects the air from the center line region, the port-side region, andthe starboard-side region. The restraining section includes a rollerprovided in the center line region. The roller rotates around arotational axis parallel to a ship width direction such that a surfaceflow of the air in the center line region is accelerated toward a sternof the ship.

An air lubrication method for a ship according to a second aspect of thepresent invention includes ejecting air from a ship bottom of the ship,and restraining a thickness of an air layer covering a center lineregion of the ship bottom from being relatively reduced.

The ship bottom includes a port-side region on a port side with respectto the center line region, and a starboard-side region on a starboardside with respect to the center line region. N central air outlets areprovided in the center line region. N port-side air outlets are providedin the port-side region. N starboard-side air outlets are provided inthe starboard-side region. Another central air outlet is provided in thecenter line region. The N is an integer equal to or more than 1. Theejecting includes ejecting the air from the central air outlets, theport-side air outlets, and the starboard-side air outlets. Therestraining includes ejecting air from the other central outlet.

The ship bottom includes a port-side region on a port side with respectto the center line region, and a starboard-side region on a starboardside with respect to the center line region. The ejecting includesejecting the air from the center line region, the port-side region, andthe starboard-side region. The restraining includes restraining movementof the air from the center line region to the port-side region by a wallsurface, and retraining movement of the air from the center line regionto the starboard-side region by a wall surface.

The ship bottom includes a port-side region on a port side with respectto the center line region, and a starboard-side region on a starboardside with respect to the center line region. The ejecting includesejecting the air from the center line region, the port-side region, andthe starboard-side region. The restraining includes accelerating asurface flow of the air toward a stern in the center line region.

The present invention provides an air lubrication device for a ship andan air lubrication method for a ship, capable of covering the entireship bottom with a layer of air of uniform thickness.

BRIEF DESCRIPTION OF DRAWINGS

The above objects, other objects, effect, and characteristics of thepresent invention will be more clarified from the description ofembodiments together with the attached drawings.

FIG. 1A is a side view showing a ship having a conventional shipfriction resistance reducing apparatus;

FIG. 1B is a bottom view of the ship having the conventional shipfriction resistance reducing apparatus;

FIG. 2 is a bottom view showing a ship according to a first embodimentof the present invention;

FIG. 3 is a conceptual diagram showing streamline distribution in thevicinity of a ship bottom of the ship according to the first embodiment;

FIG. 4A is a bottom view of a ship according to a second embodiment ofthe present invention;

FIG. 4B is a sectional view of the ship according to the secondembodiment;

FIG. 5A is a bottom view of a ship according to a third embodiment ofthe present invention;

FIG. 5B is a sectional view of the ship according to the thirdembodiment;

FIG. 6A is a bottom view of a ship according to a fourth embodiment ofthe present invention; and

FIG. 6B is a conceptual diagram for showing a rotational direction of aroller provided to the ship according to the fourth embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

An air lubrication device for a ship and an air lubrication method for aship according to the present invention will be described below withreference to the attached drawings.

First Embodiment

A ship according to a first embodiment of the present invention will bedescribed with reference to FIG. 2. The ship has a ship body 10 and anair lubrication device 20. The ship body 10 has a bow 11, a stern 12, aship bottom 13, port 14, and starboard 15. A ship length direction and aship width direction of the ship body 10 are indicated by X and Y,respectively. The ship bottom 13 includes a center line region 13 a, aport-side region 13 b on the side of the port 14 with respect to thecenter line region 13 a, and a starboard-side region 13 c on the side ofthe starboard 15 with respect to the center line region 13 a. The centerline region 13 a extends in the ship length direction X along a centerline CL of the ship body 10. The port-side region 13 b and thestarboard-side region 13 c extend in the ship length direction X to putthe center line region 13 a therebetween.

The air lubrication device 20 has an air ejecting unit 30 for ejectingair from the ship bottom 13 into water, and a restraining section 40which restrains the thickness of a layer of air that covers the centerline region 13 a from being relatively reduced. The air ejecting unit 30has a central air outlet 31 (hereinafter, to be referred to as an airoutlet 31) provided in the center line region 13 a, a port-side airoutlet 32 (hereinafter, to be referred to as an air outlet 32) providedin the port-side region 13 b, and a starboard-side outlet 33(hereinafter, to be referred to as an air outlet 33) provided in thestarboard-side region 13 c. The air outlet 31 is positioned on thecenter line CL. The air outlets 31, 32, and 33 are arranged on the sideof the bow 11 of the ship bottom 13. The position of the air outlet 31in the ship length direction X is different from those of the airoutlets 32 and 33 in the ship length direction X. In order to eject airinto water, each of the air outlets 31, 32, and 33 has a slit holeextending into the ship width direction Y, or a group of small holesarranged in the ship width direction Y. During navigation of the shipaccording to the present embodiment, the air ejecting unit 30 ejects airfrom the air outlets 31, 32, and 33 into water. Since a layer of airejected from the air outlets 31, 32, and 33 covers the ship bottom 13,friction resistance of the ship body 10 can be reduced.

The restraining section 40 includes central air outlets 41 (hereinafter,to be referred to as air outlets 41) provided in the center line region31 a. The air outlets 41 are arranged on the center line CL on the sideof the stern 12 with respect to the air outlet 31. In order to eject airinto water, the air outlets 41 each have a slit hole extending into theship width direction Y, or a group of small holes arranged in the shipwidth direction Y. The air outlets 41, and the air outlets 31 and 41 arearranged away from each other in the ship length direction X. Therestraining section 40 controls air to be ejected from the air outlet 41into water.

Referring to FIG. 3, effect of the present embodiment will be described.FIG. 3 is a conceptual diagram showing a streamline distribution in thevicinity of the ship bottom 13. In some ship types, streamlines SLextend outwardly. Therefore, when the restraining section 40 does noteject air from the air outlets 41 into water, the thickness of the layerof air covering the center line region 13 a becomes relatively thin,compared with the thickness of the layer of air covering the port-sideregion 13 b or the starboard-side region 13 c. In the presentembodiment, since the restraining section 40 ejects air from the centerline region 13 a into water, an amount of air ejected from the centerline region 13 a is relatively increased, so that the thickness of thelayer of air covering the center line region 13 a is controlled to berestrained from being relatively reduced.

It should be noted that a single air outlet 31, 32, and 33 may beprovided as shown in FIG. 2, or, a plurality of air outlets 31, 32, and33 may be provided for every plural pieces. The two air outlets 41 maybe provided as shown in FIG. 2, or, alternatively, only a single airoutlet 41, or three and more air outlets 41 may be provided.

Second Embodiment

The ship according to a second embodiment of the present invention willbe described with reference to FIG. 4A. The ship according to the secondembodiment is the same as the ship according to the first embodiment,excluding the following point. The restraining section 40 according tothe present embodiment has gas holding plates 42 and 43. The gas holdingplate 42 is provided between the center line region 13 a and theport-side region 13 b, to extend into the ship length direction X. Thegas holding plate 43 is provided between the center line region 13 a andthe starboard-side region 13 c to extend into the ship length directionX. In the present embodiment, the gas holding plates are not provided onboth outsides of the ship bottom 13 (the outside of the port-side region13 b and the outside of the starboard-side region).

Referring to FIG. 4B, the gas holding plates 42 and 43 project downwardfrom the ship bottom 13. The gas holding plate 42 has a port-side wallsurface 42 a directed inward (hereinafter, to be referred to as a wallsurface 42 a). The gas holding plate 43 has a starboard-side wallsurface 42 b directed inward (hereinafter, to be referred to as a wallsurface 42 b). The wall surfaces 42 a and 43 a extend into the shiplength direction X. The wall surface 42 a limits movement of air fromthe center line region 13 a to the port-side region 13 b. The wallsurface 43 a limits movement of the air from the center line region 13 ato the starboard-side region 13 c. Therefore, the thickness of the layerof air covering the center line region 13 a is controlled to berestrained from being relatively reduced.

Third Embodiment

The ship according to the third embodiment of the present invention willbe described with reference to FIG. 5A. The ship according to the thirdembodiment is the same as the ship according to the first embodiment,excluding the following point. The restraining section 40 according tothe present embodiment has a groove section 44 formed in a center lineregion 13 a. The groove section 44 extends in a ship length direction X.The air outlet 31 is provided in a bottom surface 44 a of the groove 44.

Referring to FIG. 5B, the groove section 44 has a port-side wall surface44 b (hereinafter, to be referred to as a wall surface 44 b), which isprovided between the center line region 13 a and the port-side region 13b and which is directed inward, and a starboard-side wall surface 44 c(hereinafter, to be referred to as a wall surface 44 c), which isprovided between the center line region 13 a and the starboard-sideregion 13 c and which is directed inward. The wall surfaces 44 b and 44c extend in the ship length direction X. The wall surface 44 b limitsmovement of air from the center line region 13 a to the port-side region13 b. The wall surface 44 c limits movement of air from the center lineregion 13 a to the starboard-side region 13 c. Therefore, the thicknessof the layer of air covering the center line region 13 a is restrainedfrom being relatively reduced.

Fourth Embodiment

The ship according to a fourth embodiment of the present invention willbe described with reference to FIG. 6A. The ship according to the fourthembodiment is the same as the ship according to the first embodimentexcluding the following point. The restraining section 40 according tothe present embodiment includes rollers 45 provided in the center lineregion 13 a. The rollers 45 are arranged on the center line CL on theside of the stern 12 compared with the air outlet 31. The rollers 45 andthe air outlet 31 and the roller 45 are arranged away from each other ina ship length direction X. The roller 45 partly exposed from an opening13 d formed in the center line region 13 a. A driving unit (not shown)rotates the roller 45 around a rotational axis S parallel to the shipwidth direction Y.

Referring to FIG. 6B, the rollers 45 rotate around the rotation axes Sso that a surface flow of the center line region 13 a is acceleratedtoward the stern 12. Since the rollers 45 accelerate the surface flow ofthe center line region 13 a toward the stern 12, a flow velocity in thecenter line region 13 a is increased. Therefore, the thickness of thelayer of air covering the center line region 13 a is controlled to berestrained from being relatively reduced.

The two rollers 45 may be provided as shown in FIG. 6A, or,alternatively, a single roller 45, or three and more rollers 45 may beprovided.

The air lubrication device 20 according to the above embodiments iseffective not only for full ships but also for slender ships.

Although the present invention has been described above with referenceto the embodiments, the present invention is not limited to the aboveembodiments. Various changes may be added to the above embodiments, andthe embodiments may be combined. For example, the air outlets 31, 32,and 33 may be replaced by a single air outlet formed to lie across theport-side region 13 b, the center line region 13 a, and thestarboard-side region 13 c.

1. An air lubrication device of a ship, comprising: an air ejecting unitconfigured to eject air from a ship bottom of said ship; and arestraining section configured to restrain a thickness of a layer of theair which covers a center line region of said ship bottom from beingrelatively reduced.
 2. The air lubrication device according to claim 1,wherein said ship bottom comprises: a port-side region on a port side ofsaid center line region; and a starboard-side region on a starboard sideof said center line region, wherein said air ejecting unit comprises: Ncentral air outlets provided in said center line region; N port-side airoutlets provided in said port-side region; and N starboard-side airoutlets provided in said starboard-side region, wherein said N is aninteger equal to or more than 1, and wherein said control sectioncomprises another central air outlet provided in said center lineregion.
 3. The air lubrication device according to claim 1, wherein saidship bottom comprises: a port-side region on a port side of said centerline region; and a starboard-side region on a starboard side of saidcenter line region, wherein said air ejecting unit ejects the air fromsaid center line region, said port-side region, and said starboard-sideregion, and wherein said restraining section comprises: a port-side wallsurface provided between said center line region and said port-sideregion to retrain movement of the air from said center line region tosaid port-side region; and a starboard-side wall surface providedbetween said center line region and said starboard-side region toretrain movement of the air from said center line region to saidstarboard-side region.
 4. The air lubrication device according to claim1, wherein said ship bottom comprises: a port-side region on a port sideof said center line region; and a starboard-side region on a starboardside said center line region, wherein said air ejecting unit ejects theair from said center line region, said port-side region, and saidstarboard-side region, wherein said restraining section comprises aroller provided for said center line region, and wherein said rollerrotates around a rotation axis parallel to a ship width direction suchthat a surface flow of the air in said center line region is acceleratedtoward a stern of said ship.
 5. An air lubrication method of a ship,comprising: ejecting air from a ship bottom of said ship; andrestraining a thickness of an air layer which covers a center lineregion of said ship bottom of ship, from being relatively reduced. 6.The air lubrication method according to claim 5, wherein said shipbottom comprises: a port-side region on a port side of said center lineregion; and a starboard-side region on a starboard side of said centerline region, wherein N central air outlets are provided in said centerline region, N port-side air outlets are provided in said port-sideregion, N starboard-side air outlets are provided in said starboard-sideregion, and another central air outlet is provided for said center lineregion, wherein said N is an integer equal to or more than 1, whereinsaid ejecting comprises ejecting the air from said central air outlets,said port-side air outlets, and said starboard-side air outlets, andwherein said restraining comprises ejecting air from said anothercentral air outlet.
 7. The air lubrication method according to claim 5,wherein said ship bottom comprises: a port-side region on a port side ofsaid center line region; and a starboard-side region on a starboard sideof said center line region, wherein said ejecting comprises ejecting theair from said center line region, said port-side region, and saidstarboard-side region, and wherein said restraining comprises:constraining movement of the air from said center line region to saidport-side region by a port-side wall surface provided between saidcenter line region and said port-side region; and retraining movement ofthe air from said center line region to said starboard-side region by astarboard-side wall surface provided between said center line region andsaid starboard-side region.
 8. The air lubrication method according toclaim 5, wherein said ship bottom comprises: a port-side region on aport side of said center line region; and a starboard-side region on astarboard side of said center line region, wherein said ejectingcomprises ejecting the air from said center line region, said port-sideregion, and said starboard-side region, and wherein said restrainingcomprises accelerating a surface flow of the air toward a stern of saidship in said center line region.